The present invention relates to a vinyl chloride resin-based composition suitable for preparing jackets of floppy discs by molding or, more particularly, the invention relates to a resin composition excellent in workability in molding, heat-resistance, tensile strength and dimensional stability.
A floppy disc jacket is a cover casing in a square form used to envelop a floppy disc in the form of a thin circular disc which should be protected from mechanical damages and contamination with dusts. The floppy disc is inserted into the disc-driving deck of a computer or other electronic instruments as contained in a jacket therefor.
Conventionally, copolymers of vinyl chloride and vinyl acetate have been used principally as the material of floppy disc jackets taking advantage of the good workability in shaping by molding and other advantageous properties of the copolymeric resin though not without a requirement for further extending the durability of the incessant use of such a floppy disc and jacket under various environmental conditions along with the recent trend of increasing prevalence of electronic office appliances such as office computers, personal computers, word processors and the like. For example, miniature-sized floppy discs of space-saving type with a diameter of 3.5 inches have been developed and manufactured to comply with the prevailing compactness of personal computers and the like. Such a small floppy disc of course requires reduction of size of the jacket therefor. This trend requires more and more increased flowability of the resin composition in molding and also requires increase of heat resistance against thermal effect from the disc driving decks as well as increase of the dimensional stability and the mechanical strength of the jacket such as abrasion resistance, tensile strength and the like in order to ensure good operability of the floppy disc.
Recently, attempts are being made in order to improve the heat resistance of floppy disc jackets to comply with the above mentioned requirements by using homopolymeric polyvinyl chloride resins, polymer blends of a homopolymeric vinyl chloride resin and a post-chlorinated polyvinyl chloride and the like instead of the copolymers of vinyl chloride and vinyl acetate, but they are inferior in the workability in moding and in the mechanical strength despite the insufficient improvement thereby in the heat resistance.